1. Field of the Invention
This invention relates to the stabilization of mixtures containing hydrocarbonaceous solids, oil and water. More specifically this invention relates to the stabilization of hydrocarbonaceous solid-oil-water mixtures by the addition of an aluminate, silicate, aluminosilicate or a combination of these compounds.
2. Description of the Prior Art
The major fuel employed by industrialized countries throughout the world is oil. Oil is feared to be a soon depleted resource. Since the early 1970's, the cost of oil has risen dramatically due to increased demand, price fixing cartels and increased exploration and production costs. In recent years there has been significant interest in replacement fuels for oil. Since coal is considerably less expensive and in abundant supply throughout the world, coal is expected to replace oil in many applications. However, such a conversion from oil to coal would require large expenditures of capital in order to replace existing oil burning systems with systems designed for coal.
An alternative to the replacement of oil systems is the use of coal-oil mixtures. Slurries of pulverized coal in oil exhibit handling characteristics similar to oil and can be transported, stored and burned in existing equipment designed for oil. A coal-oil mixture is less expensive than oil and can be utilized with no additional expenditures.
Coal-oil mixtures are not new; the first patent for coal-oil mixtures issued in 1879. However, since oil has traditionally been an abundant and inexpensive fuel, there has seldom existed a serious commercial interest for coal-oil mixtures, except during times of oil shortages.
In recent years, slurries of coal, heavy fuel oil and water have been investigated for use in industrial furnaces. However, at the elevated storage temperature necessary to reduce the oil viscosity, the coal tends to settle out of solution, giving the mixture a short life and questionable utility. Continuous mixing of the slurry maintains coal dispersement but is not usually possible or practical. Mechanical grinding or ball milling of the coal to effect a reduction of particle size, reduces the rate of precipitation, but is expensive and inefficient. The most feasible means of stabilizing such slurries has been through the use of additives.
Additives of varying chemistry and mechanisms have been tested over the years. Most proposed additives or stabilizers has been surface active agents with limited effectiveness. In recent years, the search for more effective additives have produced several potential additives yielding good stabilization of coal-oil-water mixtures. In spite of these recent advances, extensive research continues for new and better stabilizing agents.